Electrical measurements of synthetic channel-forming derivatives of alamethicin show how structural changes alter conductance changes. Such data, relevant at nearly the molecular level, add considerably to our understanding of the mechanism by which alamethicin induces conductance in black lipid membranes. We have presently synthesized two derivatives of alamethicin. The synthesis confirms that the peptide is linear and not cyclic as previously supposed and shows that a simple tansposition of residues at the C-terminus substantially alters the single channel conductances without radically altering the macroscopic conductance properties.